For the use of activated coke in a heaped or loose bed through which a medium to be treated must flow, the activated coke must be in the form of a granulate providing an adequate void volume for the medium which is to flow therethrough. Particularly when treating flue gases for desulphurizing and also for removing nitrogen compounds, these void volumes between the granulates are of considerable importance in order to attain the desired material exchange or the adsorption of noxious substances on the activated coke by intensive contact of the gas molecules with the surface of the activated coke over the shortest possible distance. The size of the granules determines the particular local void volume in the bed. In spite of the desirability of having relatively large voids in the bed, the activated coke granulates are conventionally manufactured and used with relatively small dimensions of the order of several mm. The reason for this is essentially that the manufacture of activated coke is relatively expensive and the material exchange or the adsorption takes place only in a relatively thin surface layer of the granulates. Accordingly, smaller sized granulates, requiring smaller amounts of activated coke afford a larger surface area than granulates of larger diameters. Moreover, the manufacture of granulates of larger diameters and having the required strength involves problems, particularly since when using such granulates in beds or heaps they are subjected to considerable and substantially varying pressure, in particular if the heaped materials or beds are moved through a duct or the like.